Smartphone fast charging: Balancing speed, power, and battery life
Does charging power affect the charging rate of smartphone batteries? Yes, but it is not the only factor determining the speed of this process. Let's take a closer look at why the charger's power is so important. What power is needed for a smartphone to charge "quickly"?
Manufacturers of electronic equipment are increasingly equipping their devices with fast charging features, which are extremely useful for devices charged daily, like cellphones. Many of us know the situation when, before leaving the house, we notice that our smartphone's battery is almost dead. At such moments, the advantages of fast charging become most noticeable. It is important to understand what impact charging power has on the charging time of a phone. The explanation is provided below.
Charging power of a battery - what does it depend on?
The entire process depends on the applied technology and USB standard, where power measured in watts (W) tells us how much energy can be delivered to the device.
Phone charging is most often done using a USB cable. Older standards offered only 2.5 W, resulting in charging times of 2-3 hours. Back in the days before smartphones, batteries had significantly smaller capacities.
With the advent of the USB 3.0 standard, charging power increased to 4.5 W. Today, even standard USB chargers have higher performance, with a voltage of 5 V and a current of 2 A, providing a charging power of 10 W. It is now difficult to find a new smartphone model that does not offer at least this level of charging power.
The USB Type-C technology allows for greater power due to a current of 3 A, which at 5 V gives 15 W. Greater power, however, requires fast charging technology. Even phones supporting maximum charging of 18, 20, or 25 W, like the Samsung Galaxy S24, use this technology.
Fast charging technologies - what do we know about them?
The latest smartphones often offer charging power of 45, 67, 80, and even over 100 W. Leaders in this field achieve over 200 W. Higher power accelerates charging but generates heat and may lead to faster battery wear.
Various fast charging technologies use protocols to safely charge at high currents, with popular ones such as:
What factors influence the battery charging time?
- Power Delivery (10 to 100 W), developed since 2012
- Quick Charge (up to 27 W), designed by Qualcomm
- SuperVOOC (up to 240 W), used in smartphones from Oppo, OnePlus, realme, and Vivo
- Huawei SuperCharge
- MediaTek Pump Express
Combining technologies allows for increased charging power.
Charging power influences battery charging speed, although crucial are also the battery capacity and the level of its discharge. A larger battery takes longer to charge at the same power. Compatibility of all the used charging accessories is also important, including the smartphone, charger, and cable. The power source, such as a power bank or laptop, also has its limitations.
How long will it take to charge a smartphone?
The weakest element in the charging set limits us, so even using a super powerful charger will not speed up the process if the smartphone does not support it.
To calculate the theoretical charging time, a mathematical formula can be used: charging time (in minutes) is the battery capacity (in Wh) divided by charging power (in W), multiplied by 60 minutes.
Assume the battery has a capacity of 5000 mAh (about 18.5 Wh at 3.7 V). Using different charging powers, the charging time is as follows:
How long will phones charge at specific charging powers?
- 18 W - about 62 minutes
- 25 W - 45 minutes
- 33 W - 33 minutes
- 45 W - 25 minutes
- 67 W - 17 minutes
- 80 W - 14 minutes
- 120 W - a little over 9 minutes
- 240 W - 5 minutes
In practice, the charging time may be longer due to power losses or software limitations that regulate power based on increasing temperature. It's worth checking the manufacturers' information, e.g., Xiaomi Redmi Note 9 fully charges in 153 minutes (18 W), and Xiaomi Redmi Note 11 in 60 minutes (33 W). Models supporting 67 W, like Xiaomi Redmi Note 12 Pro, achieve full charge in about 46 minutes, and the fastest solutions like Xiaomi Redmi Note 13 Pro+ with 120 W charging take 19 minutes.
Fast charging and battery life
Even among the products of the same manufacturer, differences can be significant due to the used technologies and specifications.
Finally, it is worth mentioning the impact of fast charging on battery longevity. The heat generated by high power can reduce the lifespan. Manufacturers assure that fast charging is safe, and the battery capacity may decrease to about 80% after 3-4 years. In most cases, replacing the battery is a relatively inexpensive option.
In summary, fast charging is a great convenience, especially in emergency situations. It's important to use all the parts of the set properly and compatibly.
